The present invention relates to a light control apparatus for a stop-cum-shutter to be mounted in an optical apparatus, such as a still camera, a video camera and an interchangeable lens.
As an optical apparatus, such as a digital camera, has been made smaller, a smaller shutter unit and a smaller stop unit are required to be mounted on it. A light control apparatus (shutter-cum-stop unit) is known which serves as both a shutter and a stop, and makes the optical apparatus smaller than a combination of a shutter unit and a stop unit separately.
Japanese Patent Application, Publication No. 2002-55375 discloses a stop-cum-shutter unit that includes a pair of motors, and a pair of stop-cum-shutter blades driven by these motors. As one motor is electrified, the stop-cum-shutter unit drives both stop-cum-shutter blades to a position that forms a predetermined aperture. As the other motor is electrified while the stop state is maintained, both stop-cum-shutter blades acts as a shutter. The disclosed stop-cum-shutter unit switches actions of these two motors, and sets the apertures to two predetermined apertures and release aperture. In other words, the unit acts as a shutter as well as selecting plural apertures.
However, the above conventional stop-cum-shutter unit in which one motor drives two stop-cum-shutter blades and forms an aperture has difficulties in making the aperture shape circular and making the stop multistage. In other words, the above conventional stop-cum-shutter unit provides only three apertures, a release aperture, an aperture driven by one motor, and another aperture driven by the other motor.
One known method for increasing the number of stop stages and make circular the stop shape is that a stepping motor drives plural stop blades using another component, such as a ring member. However, use of the ring member increases the number of components, and makes the apparatus large. In addition, the stepping motor is unsuitable for quick shutter actions of plural stop blades connected to the ring member. The high-speed shutter action needs a dedicated shutter blade and a motor.
Moreover, the above conventional stop-cum-shutter unit uses the same type of actuators that enable each of the two motors to drive the stop and the shutter. It is therefore difficult to form a suitable structure for both the stop action and the shutter action.